This application is a Re-issue of Ser. No. 08/193,187 filed on Jun. 3, 1994 now U.S. Pat. No. 5,602,952.
This invention relates to the packaging of fibre optic components. The invention is described herein with particular reference to the packaging of optical fibre couplers but it will be readily appreciated that the principles of the invention are readily applicable to the packaging of any fibre optic component.
Optical fibre couplers are presently supplied in a package which is designed both to physically, protect the component and to prevent the ingress of moisture and other contaminants to the component. In one known assembly, the coupler is disposed in an inner cylindrical housing formed of two half silica tubes which are machined to tight dimensional tolerances. These half tubes are brought together and attached together with adhesive. The resultant capsule includes respective adhesive deposits which serve to anchor the optical fibre component to the inner surface of the capsule and to seal the ends through which the fibres extend. Additional adhesive may be applied to the ends of the capsule to stabilise the fibres over a wide temperature range. The capsule is placed within a stainless steel outer casing which is in turn filled with an elastomer compound. The stainless steel outer casing is provided to give additional strength and protection to the optical component assembly.
Optical fibre couplers are required to have lifetimes approaching 40 years and to withstand extensive environmental variations. Even though the silica capsule is sealed with adhesive, it has been found through intensive simulated environmental testing that these adhesives are not consistently impervious to moisture over extended periods of time. Test samples have been detected where moisture has ingressed the capsule and affected coupler performance.
It is not possible to provide a hermetic glass-metal seal with the outer metal casing because of a mismatch of thermal expansion coefficients between most metals and silica
It is accordingly an object of the invention to provide an arrangement for packaging optical fibre components which provides improved sealing against moisture ingress relative to presently known arrangements but which does not unacceptably increase manufacturing costs.
In one aspect, the invention provides a fibre optic component package comprising:
a fibre optic component package comprising:
one or more fibre optic components;
an inner housing supporting the component(s), one or more optical fibres associated with the component(s) extending from the housing; and
a layer which is substantially impervious to moisture including water vapour and which encloses said inner housing, said layer including a sheet of substantially moisture impervious flexible material wrapped about the housing and a substantially moisture impervious sealant adhesive which serves to bond said sheet of flexible material and fills at least those regions at edges of said sheet of flexible material.
The invention further provides, in another aspect, a method of packaging a fibre optic component comprising:
supporting the component in an inner housing, with one or more optical fibres associated with the component extending from the housing; and
enclosing said housing in a layer which is substantially impervious to moisture including water vapour, said layer including a sheet of substantially moisture impervious flexible material wrapped about the housing, and a substantially moisture impervious sealant adhesive which serves to bond said sheet of flexible material and fills at least those regions at edges of said sheet of flexible material.
The sheet is preferably a metal foil of any suitably compliant metal, for example tin, nickel, gold, aluminium, monel or an appropriate alloy. The foil is advantageously of a thickness in the range 0.01 to 50 micron. The foil is preferably wrapped about the inner housing so as to be overlapped longitudinally of the housing.
In a practical embodiment, the inner housing may be of generally tubular form, e.g. a capsule formed from two half robes of silica or other appropriate material.
Adhesive means is preferably provided to maintain the housing and optical fibres as an assembly. Where the inner housing is a robe, this adhesive means preferably includes adhesive. deposits to seal the ends of the tube.
The package may further comprise an outer casing, e.g. a tubular casing, of material such as stainless steel, selected to provide physical protection for the package. The assembly of the inner housing and the surrounding moisture impervious layer may be retained in the casing in a suitable Sing such as silicone elastomer.
The sealant adhesive is preferably an epoxy compound.